Sear release for an automatic firearm



Jan. 19, 1960 R. AMSLER SEAR RELEASE FOR AN AUTOMATIC FIREARM Filed April 22, 1957 SEAR RELEASE FOR AN AUTOMATIC FIREARM Rudolf Amsler, Neuhausen am Rheinfall, Switzerland, assignor to Schweizerische Industrie-Gesellschaft, Neuhausen am Rheinfall, Switzerland Application April 22, 1957, Serial No. 654,374

Claims priority, application Switzerland August 28, 1956 3 Claims. (Cl. 89-149) The present invention relates to an automatic firearm having a breech head and a follow-up member movable relative thereto under the action of a closure spring wherein the percussion pin is guided movably.

From known embodiments the one according to the present invention is distinguished by a spring-loaded hammer for the percussion pin which is controlled by a sear, in turn controlled by the follow-up member.

In the-drawing an embodiment of the invention and a modification thereof are diagrammatically illustrated by way of example, wherein:

Fig. 1 is a partial longitudinal section of one embodiment,

Fig. 2 is a corresponding part section of a modified embodiment, and

' Fig. 3 is a section on the line 3-3 of Fig. 1.

In the drawing 1 denotes the elongated receiver which at its forward end carries the barrel 14 and is closed at its rear by the cap piece 7. In this receiver 1 the multipiece breech bolt or body is guided axially movably under the action of the blow back gas pressure when firing a cartridge on the one hand, and of a closing spring 6 on the other hand. This breech bolt or body comprises a breech head 2 and a follow-up member 3. The percussion pin 4 is resiliently coupled to the followup member by a spring 5, by which it is retracted and pushed back.

The breech head 2 has mutually opposite recesses 8 wherein locking rollers 9 are housed transversely movable with respect to the longitudinal axis of the receiver. The same can be forced by the frusto-conieal forward end of the follow-up member 3 outward in a lateral direction into the locking grooves 10, when this end is moved forward.

On the follow-up member a control groove 11 running in the longitudinal direction is provided which is closed at its rear end by an abutmentor shoulder-face 13. The receiver is provided with an opening 13' in registry wtih the groove 11 for the passage of the T-headed portion of the connector 12. Into this groove projects the nose 12 of a connector 15 which is mounted pivotally about a pin 16 on the rear end of the receiver 1. A compression spring 17 bears on a sear plate 19 which is pivotally mounted at 21 and against the forward end of which abuts a further nose 18 of the connector 15. When the connector 15 is turned about the pin 16 in the counterclockwise direction against the action of the spring 17 by the abutment face 13 abutting the nose 12, the sear plate 19 and a sear 20 fixed to the same is likewise turned in the same sense about the pin 21. The forward end of the sear 20 thereby slides off the control nose 22 of the hammer 23 which is consequently released for being turned about the axle 24. This turning movement is effected by a strong compression spring 25 which tends to turn the hammer in the counter-clockwise sense. By this turning movement the hammer acts on the rear end of the percussion pin 4 when the multi-part bolt is closed which is thereby struck and moved in the forward di- Patented Jan. 19, 1960 rection. The firing pin 4 is connected to the follow-up portion of the multi-part breech bolt by a pin and slot connection including a transverse pin 25 which is carried by the follow-up portion of said bolt and is received in a slot 26 on the firing pin.

- The manner of operation is as follows:

The multi-piece breech bolt or body is in its rear end position into which it has been brought by the blow back gas pressure from a fired cartridge. The recoil closing spring 6 is loaded, and the nose 12 of the sear is at the forward end of the control groove 11. Und the pressure of the recoil closing spring the breech body moves forward into battery position, inserting thereby a cartridge in the usual manner into the barrel 14. The follow up member, which is movable relative to the head piece 2, reaches the forward end position shortly after the latter and forces as far as necessary the rollers 9 into the locking grooves 10. Shortly before the follow-up member 3 has reached its forward end position, the abutmentor shoulder-face 13 abuts the nose 12 of the connector 15. The latter is turned in the counterclockwise sense, and the sear 20 releases the hammer 23. The same strikes an abutment face 4a within a slot 26 of the percussion pin 4 under the action of the. spring 25' whereby the shot is fired. By the pressure exerted on the sleeve by the explosion gases forcing the cartridge case rearwardly a blow back pressure is applied to the breech head 2. This breech head bears on rollers 9 which in turn bear on the frusto-conical forward end of the follow-up member 3. The latter accordingly moves back until the rollers move inward. Then the multi-piece breech bolt or body can move back as a whole whereby the recoil closing spring 6 is loaded again. When the cartridge is fired the blow back force of the cartridge case exerts rearward pressure on the bolt head 2 which moves'the rollers 9 rearwardly and inwardly. This force also moves the follow-up device rearwardly and permits the rollers 9 to move out .of engagement with the shallow recesses 10.

The construction described assures that the follow-up piece 3 must have reached a predetermined forward position before the hammer is released. The multi-part breech bolt or body as a whole is locked by the locking rollers 9 before the firing of a shot takes place when the breech body is not completely locked, for example owing to fouling.

The spring 6 could alternatively be replaced by a pair of springs 6a lying on diametrically opposite sides of the percussion pin 4 and acting directly on the follow-up member 3.

While I have herein described and illustrated in the accompanying drawing what may be considered typical and particularly useful embodiments of my said invention, I wish it to be understood that I do not limit myself to the particular details and dimensions described and illustrated, for obvious modifications will occur to a person skilled in the art.

What I claim as my invention and desire to secure by Letters Patent is:

1. An automatic firearm comprising in combination: a receiver, a multi-part breech bolt reciprocab'ly mounted in said receiver including a breech head and a follow-up member slidably mounted in said breech head, a recoil spring biasing said follow-up member in a direction toward said breech head, a firing pin movably guided in said follow-up member and extending through a central bore of said breech head, a pin and slot connection between said firing pin and follow-up member to permit limited movement therebetween, -a firing pin retracting spring located in said follow-up member and exerting rearward pressure on said firing pin, a sear plate pivotally connected to said receiver having a sear, a connector 3 also pivoted to said receiver and having a-T-shaped head with one portion of said T-shaped head extending through an opening in said receiver to be engaged by said follow-up member when the same reaches the limit or its forward travel and the other end ofsaid T-shaped head to simultaneously engage said sear plate, a hammer having a sear notch engaged by said scar and releasable upon forward movement of'said follow-up member to its battery position to strike said firing pin and a compression spring for operating said hammer 'when said sear is released from said sear notch.

2. An automatic firearm comprising in combination:

'a receiver, a multi-part breech bolt including a breech head and a follow-up member movably mounted .with respect to said receiver and'to one another, a recoil "spring biasing the follow-up member toward said breech head, a firing pin movably guided in said follow-up member and extending through a central bore of said breech head, a pin and slot connection between said firing 'pin and follow-up member, a hammer pivoted to saidreceiver having a scar notch, a spring for urging 'said "hammer into forcible striking engagement with said fir.- "ing pin, a sear plate pivoted to said'receiver having a scar adapted to be received in'said notch, spring'means for holding said sear in said notch, a T-shaped connector including an elongated arm pivoted to said receiver and having oppositely extending extensions on one end thereof "3. An automatic firearm comprising in combination: a receiver, a multi-part breech bolt including a breech head and a follow-up member reciprocably mounted in said receiver and movable 'with respect to one another,

a recoil spring biasing said'follow-up member toward said breech head, a firing 'p'in'movably guided in said follow-up member and extending through a central bore of said breech head, aspring loaded hammer pivoted to said receiver adapted to strike the rearend of said'firing pin, a searplatepivoted to saidreceiver having'a sear yieldingly urged into engagement with a sear' not'chin said hammer to hold the same in its retracted-position, and a T-shaped connector pivoted to said receiver having an enlarged end'portion with oppositely directed'extensions one of. which is'adapted to project through an opening in said receiver into the path of a projection on said follow-up member, while the other projection is presented to said sear plate whereby movement "of said follow-up member in a forward direction will simultaneously release said sear from said sear notch and 'per-' mit said hammer to strike said firing pin.

References Cited in the-file of this patent UNITED STATES PATENTS I 

